Abametapir and Theophylline: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jun 30, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Abametapir
No brand names on recordTheophylline
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Abametapir is a lotion used to treat head lice. Even though it's applied to your scalp, some of it can get into your body and slow down a liver enzyme called CYP1A2. That same enzyme is what breaks down your theophylline, the medicine that helps open up your airways.
When that enzyme is blocked, theophylline can build up higher than usual. Theophylline has a narrow safety window, so even a small rise can cause side effects like a racing heartbeat, nausea, shakiness, or trouble sleeping. The good news is your care team can plan around this easily, so please talk with your pharmacist or doctor before using both.
Mechanism: Abametapir is a CYP1A2 inhibitor; theophylline is a CYP1A2 substrate. Inhibition reduces theophylline clearance, raising its exposure (AUC/Cmax).
- Direction: Increased theophylline exposure and toxicity risk.
- Evidence: Theoretical, based on abametapir's known CYP1A2 inhibition; magnitude not quantified.
- Onset: Unspecified; inhibition may persist up to ~2 weeks post-application.
- NTI concern: Theophylline has a narrow therapeutic index, so small PK shifts are clinically meaningful.
Management: Avoid CYP1A2 substrates for 2 weeks after abametapir application; if unavoidable, avoid abametapir. If co-use occurs, monitor theophylline levels and for signs of toxicity (tachycardia, tremor, nausea, seizures).
What happens
Increased exposure of CYP1A2 substrates
Interaction Deep Dive
During the 2 weeks following abametapir application, refrain from using CYP1A2 substrates. If avoiding these substrates is not possible, then abametapir should not be used 1.
Why it happens (mechanism)
Inhibition of CYP1A2-mediated metabolism by abametapir
How to manage this interaction
The main documented approach is timing and avoidance rather than a set dose change:
- Spacing: Guidance is to avoid CYP1A2 substrates like theophylline for 2 weeks after applying abametapir. If that isn't feasible, the abametapir treatment itself may be avoided.
- Keep taking your theophylline as prescribed and do not stop it on your own.
- Before using an abametapir lice treatment, tell your pharmacist or prescriber that you take theophylline so they can pick the safest plan.
- If both are used together, your team may check your theophylline level more closely and watch for side effects.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abametapir and Theophylline together?
Abametapir can raise theophylline levels by blocking the enzyme that clears it, and theophylline has little room for error. Talk to your pharmacist or doctor before using both; guidance is to avoid theophylline for 2 weeks after applying abametapir. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abametapir and Theophylline interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Abametapir and Theophylline interaction managed?
The main documented approach is timing and avoidance rather than a set dose change: Spacing: Guidance is to avoid CYP1A2 substrates like theophylline for 2 weeks after applying abametapir. If that isn't feasible, the abametapir treatment itself may be avoided. Keep taking your theophylline as prescribed and do not stop it on your own. Before using an abametapir lice treatment, tell your pharmacist… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Abametapir or Theophylline need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: XEGLYZE(TM) topical lotion, abametapir topical lotion. Dr Reddy’s Laboratories Inc (per FDA), Princeton, NJ, 2020. DailyMed
Keep reading about Abametapir
Keep reading about Theophylline
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